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    Vizio E420VL problem

    Ok i have a vizio that has an issue, i know go figure, been doing a lot of reading it would appear that these units have many problems.

    Anyway the original problem was the unit would not power on or anything. I had the power board tested and it came back as good. Had the main board tested it came back as damaged beyond repair.

    So i purchased a used board, i know big mistake, but it was the only one i could find.

    Anyway the symptoms are as follows: Power off/standby vizio symbol orange, power on vizio symbol goes white. Now the screen flashes breifly as does a blue light you can see reflecting on the back panel from the power supply. I only have a 12in green ccfl lamp and i hooked it into the output that drives the lamp and you can see that it flashes briefly as well.

    A friend of mine told me to take voltage measurements on J1 which is the main plug between the power board and the logic board, said 14 should be like 3.3, 13 should be 9.2, 12 should be 3.3 and 11 should be 2.2. Well the voltage on 12 is correct and the voltage on 11 is correct, the other two voltages are (0) zero.

    On a hunch i cut the two wire about midpoint between power board and logic board.

    I measured all 4 wires in ref to dgnd.

    With the tv plugged in but the vizio symbol in orange, which is to be standby if I understand the manual correctly, all 4 wires measured (0) zero. Which is exactly what one would expect.

    With the tv plugged in and the vizio symbol in white, also taken as the tv would normally start up, the red and orange wires from the logic board measured zero. However the red wire from the power supply side spiked up but it was two quick for my DVM to read but then it settled at like 5.38 volts, and the orange wire from the power supply ran up to about 3.37 volts.

    Now I want to add that also the back lights on the television still flashed, just one quick maybe half a second flash.

    Now what I done was hooked up the orange wire, left the red wire unhooked, measured voltage, this time I got (0) zero.

    And the final thing I done was hooked up the red wire, left the orange wire unhooked, measured voltage and I got the short spike but then again it settled down to 5.38

    What is odd is if you connect both red and orange wires, you get zero all the time.

    So now does this come back to a power board failing or the main logic board failing? would like to know how i can turn the invertor output on continuous on the power board so i could see all the lamps light behind the screen. Dont know if that is even possible.

    Thanks for reading and thanks for any and all guidance you can supply.

    #2
    Re: Vizio E420VL problem

    Well, first post good clear pictures of the boards. Voltages testing and
    then we need to know if the BL_ON (invr_on) is present when the backlights flash off. Read the LCD TV basic troubleshooting first will help you understand what the TV needs to operate.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment


      #3
      Re: Vizio E420VL problem

      So basically if i understand these guides, you turn the power on which in turn turns the invertor on, it is at that time the invertor sends the start up voltage to the lamps. if after a short period of time the invertor does not detect the proper current draw from the lamps, it shuts down. Would that be a correct assessment?

      So in the case of a 42 in tv it is looking for a certain current to be maintained once the bulbs start up. if it does not maintain then it shuts down, which is why the quick blip.

      I was looking at that CCFL page you linked and was wondering, if i tried one of the 13 watt tubes like shown, wonder if that would draw enough so that it would keep the invertor circuit on?

      Comment


        #4
        Re: Vizio E420VL problem

        "So basically if i understand these guides, you turn the power on which in turn turns the invertor on, it is at that time the invertor sends the start up voltage to the lamps. if after a short period of time the invertor does not detect the proper current draw from the lamps, it shuts down. Would that be a correct assessment?

        So in the case of a 42 in tv it is looking for a certain current to be maintained once the bulbs start up. if it does not maintain then it shuts down, which is why the quick blip. " Yes that can be symptom of bad lamps but can also be symptom of bad inverter circuits, bad power supply feeding the inverter circuits, also bad BL_ON signal that only appear for seconds instead of being there and stay there when TV is ON. The symptom can be caused more than one source of the circuits.
        This is the 2-second to black thread: https://www.badcaps.net/forum/showthread.php?t=10419
        Last edited by budm; 02-21-2014, 03:07 PM.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment


          #5
          Re: Vizio E420VL problem

          Ok Budm, heres a question concerning the CCFL backlight, a guy told me that if i were to jump the black and brown wires which are ps/on and I/O it would permanently turn on the power supply and keep the CCFL inverter on.

          I think this is a wrong statement. Because everything i have read seems to indicate that the invertor sends out the startup pulse, and like you said then starts monitoring the current, if the current does not match what it expects to see it shuts down the invertor circuit.

          Now i have opened up the back of the screen and personally inspected each lamp, they all seem to be plugs in solid, no black on the ends none broken.

          So i am curious if anyone happens to know how to figure out what kind of current draw the invertor is looking for and if the invertor can be fooled using a resistor or some other device. This way i could eliminate the back lights as the cause for the power supply shutting off the invertor.

          From my basic limited perspective on things i am thinking it is the power board that is goofy, but my friend says no it is the main logic board.

          It is really frustrating.

          Comment


            #6
            Re: Vizio E420VL problem

            Did you try turning on the TV and see if ALL the lamps come on for seconds before shutdown, the circuits also detect if the lamp fired up but not staying on or open lamp. I have no idea what the I/O pin he is talking about.
            This is some example of the detection function.
            Attached Files
            Last edited by budm; 02-24-2014, 10:35 AM.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment


              #7
              Re: Vizio E420VL problem

              Budm, I took the screen apart to observe the ccfl tubes, while it is brief, all the tubes appear to light.

              Again as i said it is less than 1 second. Quick flash.

              As to the I/O, there are 4 wires that my friend told me about that are important. All the other wires that go between the power board and the main logic board are just simply power and ground.

              The 4 signals are as follows and it is the way it is silk screened onto the power board.

              PS ON, I/O, DIM, LMP

              As first my friend told me about the voltages here, they should be PS ON = 3.3, I/O = 2.3, DIM = 2.8, and LMP = 9.1

              I checked these voltages and the 2 i do not have are DIM and LMP. Im not even sure if these signals are from the power board to the main logic board or if they are from the main logic board to the power board. I do know that when i cut these wires, voltages were present on the wires that are connected to the power board. But still the backlights do not stay lit up, all i get is a quick flash. Not quite as quick as say a camera flash, but fairly close.

              My friend says it is the main logic board, but because it is not powering the ccfl lights i am say it is the power board. SO right now just very confused in which way to proceed.

              Comment


                #8
                Re: Vizio E420VL problem

                Can we see the pictures of this power supply inverter board so I can look for more info? There are more than one version of this model.
                Which one do you have? see pictures here.
                http://www.shopjimmy.com/catalogsear...q=Vizio+E420VL
                Last edited by budm; 02-24-2014, 11:28 AM.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment


                  #9
                  Re: Vizio E420VL problem

                  Ok budm here is all the details about everything that is my tv set

                  Power supply 0500-0412-1030
                  Main Board 3642-1242-0395
                  Panel LG LC420WUH(sc)(r1)

                  Hope that all helps.

                  Comment

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